Cars and trucks include lamps to provide illumination, including headlamps, fog lamps, and daytime running lamps. Fog lamps are auxiliary lighting devices typically mounted low in the front fascia of a vehicle. Fog lamps direct light low and toward the ground to provide improved visibility during poor weather conditions. Fog lamps typically do not direct substantial amounts of light above a horizontal plane, to help prevent glare that may dazzle oncoming drivers. Typical “projector” fog lamps include a halogen light bulb surrounded by a polyellipsoidal reflector, which is covered by a glass aspheric condensing lens. When packaged into the vehicle, the bulb, reflector, and lens assembly of a projector fog lamp may extend relatively deep into the vehicle's front fascia.
Daytime running lamps (DRL), also called daytime running lights, are forward lighting devices that are intended to increase the visibility of a vehicle when its main headlamps are not be activated, such as during the day or in mixed lighting conditions. DRLs typically direct light forward, and a substantial amount of light may be directed above the horizon. As compared to light produced by fog lamps, directing light forward and above the horizon may cause additional light to reach the eyes of oncoming drivers, increasing the visibility of the DRL. Because DRLs are typically used in conditions with relatively bright ambient light, DRLs may not dazzle oncoming drivers. DRLs may produce light of similar intensity to low-beam headlamps or may produce light of lower intensity. Typical DRLs may be implemented using dedicated lamps, or by running incandescent headlamps with reduced voltage.
Light-emitting diode (LED) light sources provide an efficient light source. LEDs for automotive applications typically consume about 12 watts of electrical power in operation. LEDs also generally have much longer expected lifetimes than halogen or other incandescent light bulbs. However, LEDs differ from halogen light bulbs in several characteristics. LEDs typically produce lower amounts of luminous flux. Additionally, the longevity and light production of LEDs are both sensitive to operating temperature, requiring thermal management.